What is the most likely cause of alopecia (hair loss) in patients receiving prolonged Total Parenteral Nutrition (TPN)?

Alopecia with Prolonged Total Parenteral Nutrition

The correct answer is A: Zinc deficiency is the most common and well-documented cause of alopecia in patients receiving prolonged total parenteral nutrition. 1, 2, 3

Primary Cause: Zinc Deficiency

Zinc deficiency is the most frequently suspected and documented micronutrient deficiency causing hair loss in TPN patients, with rapid clinical responses reported from zinc therapy. 2 The mechanism is clear:

• Zinc is essential for alkaline phosphatase, a zinc-dependent enzyme with elevated activity in tissues with high proliferative activity like the hair follicle 1
• Zinc deficiency causes telogen effluvium and induces thin, brittle hair 1
• Characteristic presentation includes alopecia with seborrheic dermatitis-like lesions in areas of high sebaceous gland concentration and hyperkeratotic lesions on extensor surfaces 3

Clinical Evidence from TPN Patients

• Seven patients on TPN developed severe hypozincemia (<60 μg/dL) with characteristic skin lesions and alopecia that completely resolved when serum zinc was raised above 60 μg/dL with zinc sulfate replacement 3
• Even with trace element supplementation (2 mg/day elemental zinc), deficiency can occur - one case required increasing to 60 mg/day total zinc, with lesions improving within 2 days and complete healing within 2 weeks 4
• ICU patients on prolonged PN are at particular risk when hypermetabolic with elevated nutritional requirements, and zinc deficiency should be monitored monthly 1

Why Other Options Are Less Likely

B. Magnesium Deficiency

• No documented association between magnesium deficiency and alopecia in TPN patients 1
• Studies found no differences in magnesium levels between alopecia patients and controls 1

C. Vitamin A Intoxication

• Vitamin A excess, not deficiency, can theoretically cause hair loss, but this is not a documented complication of standard TPN 1
• The evidence relates to oxidative stress pathways, not direct toxicity from TPN formulations 1

D. Essential Fatty Acid Deficiency

• This was historically a cause but has been essentially eliminated by regular use of lipid-containing parenteral nutrition 2
• Modern TPN formulations routinely include lipid emulsions, making this deficiency rare in current practice 2

Other Micronutrient Considerations in TPN-Related Alopecia

Biotin Deficiency (Not Listed but Important)

• Biotin deficiency presents with alopecia totalis, hypotonia, and periorificial dermatitis in TPN patients 5
• Three pediatric cases showed dramatic response to biotin therapy (100 μg/day) with resolution of rash, alopecia, and neurologic findings 5
• Two adults on long-term home TPN developed severe hair loss that resolved with 200 μg biotin daily supplementation 6
• This has become rare since biotin is now routinely added to TPN, but marginal biotin status could still occur 2

Selenium Deficiency

• Alopecia in some infants on TPN has been relieved within weeks by selenium supplementation as selenite 2
• Acute selenium deficiency can cause cardiomyopathy in critically ill patients 1

Clinical Recommendations

When alopecia develops in TPN patients, check serum zinc levels immediately and supplement if deficient. 1, 2, 3 The standard approach:

• Monitor zinc levels monthly in prolonged PN, especially in hypermetabolic or critically ill patients 1
• Target serum zinc >60 μg/dL to prevent dermatologic manifestations 3
• Therapeutic zinc dosing: 60 mg/day total zinc when deficiency is documented, with clinical improvement expected within 2-14 days 4
• Ensure adequate trace element supplementation (zinc 3.27-10 mg/day in standard formulations may be insufficient) 1